It is my understanding that the game simply treats the games that are DDOSed (for those that end up getting ddosed) as not having existed (hence the reason why there is no match history for it)
Once again, I could be wrong here.
Also, the odds of you getting DDOSed more than once a week, aren't particularly large (in fact, they are...and hopefully shall remain....quite small at the moment). This is why you are given a set amount of "freebies" that you can leave a game (and as I also suggested, those freebies should recharge weekly, longer or shorter depending on whichever is deemed more favorable, but I think weekly is the golden spot personally).
The idea can further be expanded to include a set maximum amount of freebies that you can have (lets just set that to 3 for this example).
So you can leave ranked games a total of 3 times without getting in trouble (aside from the normal leaverbuster issues), and once every week, you get 1 charge back, up to a maximum of 3 charges.
Don't AFK? Well then you will have 3 freebie charges just in case that moment happens when you actually need to leave the game (or internet decides to pull an F-U moment)
The only problem that can arise from the "freebie charge" system would be the potential for abuse. You could afk from a ranked game a couple times in a week, then next week go afk for 1 game, then next week go afk for 1 game, and have no loss in LP....however, this is where leaverbuster comes in to deter people from continuously afking (and as I said before, leaverbuster does need work, but the one thing it does reliably do is tell whether or not someone is afking a lot, and honestly if someone is afking and it legitimately isn't there fault, then they should stop playing ranked until they fix whatever is causing them to afk so much, be it internet, real life, or something else entirely).